Researchers Engincan Tekin, Ming Cao, and Ajay Giri Prakash Kottapalli at the University of Groningen used the BMF microArch S240 to fabricate the first fully printed MEMS flow sensors based on actual seal whisker geometry — achieving sub-10 µm resolution in a single-step process.
The Challenge
Seals can track the hydrodynamic trails of prey through dark, deep water using only their whiskers — a capability rooted in the whiskers’ unique undulating geometry, which suppresses self-generated vibration noise and amplifies faint wake signals. Researchers at the University of Groningen’s Department of Bioinspired MEMS and Biomedical Devices set out to replicate this functionality in a functional MEMS flow sensor.
The challenge: previous biomimetic whisker sensors had relied on simplified, idealized models. The team wanted to work from high-resolution 3D scans of actual harbor seal, gray seal, and sea lion whiskers — and fabricate them with enough precision to preserve the species-specific surface undulations and elliptical cross-sections that make the geometry meaningful.
Conventional manufacturing methods couldn’t do it. They needed micron-scale additive manufacturing.
The Approach
The team turned to Boston Micro Fabrication’s microArch S240, using Projection Micro Stereolithography (PµSL) to print scaled whisker geometries from HTL resin at 10 µm layer thickness — achieving morphological fidelity that was confirmed both visually and through quantitative feature measurement.
In parallel, they fabricated a soft, compliant sensing base — an artificial follicle-sinus complex (FSC) — using a custom resin blend of PDMS-like resin and BMF’s UTL resin in a 70:30 ratio. The S240 printed the FSC, including internal microchannels just 500 µm wide with 20 µm corrugated layers, without support structures. Graphene nanoplatelet (GNP) ink was then infused into the channels via capillary action to form the piezoresistive sensing elements — completing a fully printed, functional MEMS sensor in a single workflow.
The Results
The sensors demonstrated high strain sensitivity (gauge factors of 16.57 in tension and 10.67 in compression), stable performance across 3,000 duty cycles, and the ability to detect oscillatory displacements as small as 0.5 µm at frequencies up to 70 Hz.
In comparative flow testing, sensors fitted with harbor seal and gray seal whiskers — which feature the characteristic undulating morphology — showed signal-to-noise ratios 5–10× higher than those fitted with smooth sea lion whiskers, validating millions of years of evolutionary design in a printed MEMS device.
Dive deeper into the research — read the full paper in Microsystems & Nanoengineering.
